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Am I the problem, or the mobo?

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May 5, 2010 1:05:15 AM

I have an ASUS M3A motherboard for my desktop PC. Specs are as follows:
AMD Phenom Agena 9600
4 gigs Gskill ram (not sure of speed)
ATI HD4850
OCZ StealthXstream 750W psu

My question that no one has been able to answer thus far is this: About a week ago my power supply died on me. It is the one listed. I just received a replacement today of the exact same type of psu. I have put it in and hooked everything up afaik and turn on my pc only to see that it doesn't boot. It doesn't post, there are no error beeps, but the external fans and gpu fan turn on (the gpu fan revs really high) and the CPU fan doesn't spin up at all. Is it possible that when my first PSU died that it damage another part? Maybe the mobo or ram? I know the processor is fine because I removed the fan/heatsink and powered up for about 4 seconds and I felt the processor warm up. I'm really at a loss here guys and I would love any help I can get. I hope it's something as simple as me overlooking some wire hookup somewhere.

More about : problem mobo

May 5, 2010 1:24:18 AM

Just because the psu fans spin does not mean it producing enough voltage to power the system you should try another power supply.
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May 5, 2010 4:15:25 AM

plus2plus said:
Just because the psu fans spin does not mean it producing enough voltage to power the system you should try another power supply.


Like I said in my post, the power supply is brand new now. It is the same model I had before which successfully powered my machine for a solid year and 750W is more than adequate for what I run. I just highly doubt it is the PSU unless they sent me a brand new one that is also faulty
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a b V Motherboard
May 5, 2010 4:28:04 AM

Did you plug in the 12v cpu power?

Yes, the new PSU could be defective.

Old psu could have taken out the board.
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a b V Motherboard
May 5, 2010 4:37:26 AM

Yes, when a power supply dies, it can take just about any of the other parts with it. Hard to tell which one unless you test them out one at a time, probably in another system if you can't get this one to boot.

This does sound suspiciously like what can happen if you forget to plug in the supplemental 4-pin power connector that some motherboards have (and yours happens to have as well). I've also seen it happen on systems where the video card's power cable is not hooked up or isn't seated right. Basically, either of these things can make it so the motherboard either doesn't know where to send power, or can't supply enough to a certain part. First thing I'd do is unplug and replug all the cables, unseat and reseat the video card and RAM, etc., to make sure they're hooked up right.

Also, you may want to make sure the motherboard isn't shorting to the case -- the simple way to do that is to just check that none of the screws or standoffs holding it down have come loose ... to be absolutely certain, set the guts of the whole system up on a non-conductive surface (outside of the case) and try to turn it on that way. However, since you can power it on with the CPU fan removed, I'd be less inclined to believe that as the problem and would check the cables/connections first.
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a c 156 V Motherboard
May 5, 2010 12:50:01 PM

The processor heating up does not necessarily indicate a good processor.

First:
Our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...

Pay attention to the breadboarding section where I talk about building a PC in stages to test the various parts.

If you have just a motherboard, CPU & HSF, PSU, and system speaker and you get silence; one of those three main parts are bad. Usually it is the PSU.

Try to borrow a known good PSU. A brand new, out-of-the-box untested PSU is not a known good PSU.

If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this control signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks, measuring at the back of the main power plug with the PSU plugged into the computer to put a load on the PSU.
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